Scanning force microscope having aligning and adjusting means

ABSTRACT

A scanning force microscope having a sensor head and a base wherein a moveable sample holder is housed in the base and is positioned relative to a probe housed in the sensor head, such sample being monitored by an optical deflection detection system. The detection system is configured to provide direct visual observation of the probe with respect to the sample. The mirror of the detection system is mounted in a cut away portion of a sphere and defines the axis of rotation of a kinematic mount, such providing ease of fine adjustment of the detection system. The sensor head is in communication with the base by a stage kinematic mount, such providing ease of position adjustment of the sensor head with respect to the base.

BRIEF DESCRIPTION OF THE INVENTION

This invention relates generally to scanning microscopes used to examinesuch samples as thin-film depositions and semiconductor defects. Moreparticularly, it relates to scanning force microprobes of the typehaving a probe positioned relative to a sample holder and orientationdevices for the same. Most particularly this invention describes ascanning force microscope that has an open architecture for anunobstructed view of the sample, an easy to use and intuitive alignmentmechanism of the detection system and means of locating the probe to adesired region of the sample.

BACKGROUND OF THE INVENTION

The scanning force microscope is one example in a broad category ofscanning microprobes. Types of microprobes described to date aresensitive, inter alia, to magnetic, electrical, mechanical, geometrical,thermal, electrostatic and optical properties of the sample. In generalterms, a scanning microprobe is an instrument that maps a spatiallyvarying surface property into an image. In the scanning forcemicroscope, as the sample moves in the horizontal plane relative to theprobe, the probe which is mounted on a flexible cantilever is deflecteddue to the forces between the probe and the sample's surface. For thecase of topographic imaging in the repulsive mode, the tip of thecantilever is scanned across the surface of the sample, the cantilever'sdeflection increases for peaks and decreases for valleys. The deflectionof the cantilever is monitored with an optical deflection detectionsystem. In this scheme, a laser beam from a laser diode is reflected offthe top of the cantilever onto a position sensitive photodiode. A givencantilever deflection will correspond to a specific position of thelaser beam on the photodiode. A servo loop, using the position detected,sends a correction signal to a transducer element which is connected tothe sample holder to adjust the spacing between the sample and the probein order to maintain constant force between probe and sample. Thiscorrection signal is recorded as the Z height of each point on thesample.

Most scanning force microscopes are connected to computer systems thatcreate gray-scale images to represent the height information of asample's surface. In a gray-scale image, x and y data form thehorizontal plane and z data is displayed in a linear scale in which thebrightness of the data point is directly correlated with the height ofthe surface structure. A darker data point corresponds to a lower heightvalue, while a brighter data point corresponds to a higher height value.

Another possible computer-based topographic representation isthree-dimensional image rendering of surfaces. In this representation,height is shown by superimposing the gray scale on a third(perpendicular) axis and rotating the display to an informative viewingangle. One can add a computer-generated artificial light source to castshadows that enhance the three-dimensional rendition.

An optical deflection detection system used in the prior art includes alaser positioned directly above the cantilever, so that the laser'slight directly impinges the cantilever. This is described in U.S. Pat.No. 4,935,634. The cantilever is positioned at an angle relative to thehorizontal plane so that the path of the beam reflected off thecantilever is at an angle different than the incident beam. Thereflected beam is then reflected off a fixed mirror so that the lightstrikes a detection device.

There are several disadvantages to the configuration of the prior art.Because the laser is positioned directly above the cantilever, the lineof sight to the probe and the sample is obstructed so that any visualobservation of the sample position relative to the probe can only beperformed at an oblique angle or by disassembling the apparatus.Adjustment of the probe position can therefore be a very time consumingand awkward process. Furthermore, the adjustment accuracy is degraded bythe off-axis view, particularly since the depth of field limits viewingto a narrow region.

Generally, the optical deflection detection device requires very precisepositioning because the spot on the cantilever that must be hit by thelaser beam is typically only 10 microns in diameter and the size of thelaser diode beam is about 7 microns. Therefore, fine control of theangular positioning of the beam with respect to the cantilever and thephotodetector is desirable. The mirror of the prior art, however, isfixed and therefore the detection system is difficult to adjust.Adjustment is by lateral positioning of the laser beam which maycompromise mechanical stability.

Another disadvantage of the prior art is the complexity and inaccuracyof arrangements to adjust the position of the probe relative to thesample. Because of the strict requirements for mechanical stability, itis typical to employ a kinematic mount to couple the scanner and sampleassembly to the probe and sensor head. Such arrangements requireseparate translation arrangements to permit probe positioning on thesample and typically these reduce the mechanical rigidity of theapparatus.

OBJECTS OF THE INVENTION

In light of the aforementioned problems with the prior art, it istherefore an object of the present invention to provide a scanningmicroscope in which is there are minimal physical obstructions to visualobservational adjustments of the probe with respect to the sample.

It is another object of the present invention to provide a scanningmicroprobe in which there are minimal physical obstructions to visualobservational adjustments of the laser with respect to the probe.

It is also an object of the present invention to provide a highstability optical deflection detection system having fine adjustmentcapabilities in approximately orthogonal axes making it easy to use.

Furthermore, it is also an object of the present invention to provide ascanning microscope having adjustment capabilities with two degrees offreedom, that is, independent axes of motion of the probe relative tothe sample.

SUMMARY OF THE INVENTION

The scanning force microscope of the present invention includes a sensorhead which houses the probe and the optical deflection detection systemand a base which houses the sample holder. The probe is mounted on theunderside of a flexible cantilever and a reflector is mounted on the topof the flexible cantilever or the reflector may be of material which iscoated on to the flexible cantilever or it may be that the cantileveritself is reflective, such being affixed to a tip holder rigidly mountedwithin the sensor head. The optical deflection detection system ismovably mounted within the sensor head.

The optical deflection detection system includes a laser diode whichemits light that is reflected off a mirror and directed to thereflector. The reflector in turn reflects the light to a detector, suchbeing a split detector. Feedback information regarding the position ofthe probe, that is whether the cantilever has been deflected, is sent tothe control system of a servo loop which adjusts the position of thesample holder. The feedback arrangement described herein may be optionalwherein the probe may actually provide the map of the sample,eliminating the need for a feedback arrangement.

The optical deflection detection system is arranged so that there are nophysical obstructions to viewing the probe from vertically above theprobe and the sample. The laser is positioned above and to one side ofthe probe so that the probe is visible when viewed from above. It shouldbe noted that the language of above, below and to one side used in thespecification including the claims is meant in a relative sense, and isnot intended to impart any limitations to the three dimensionalorientation which the present invention may be used.

The mirror of the deflection detection system is adjustable for finecontrol of the angular positioning of the beam with respect to thecantilever and the photodetector. To this end, the mirror is mounted ina kinematic mount, for example, in the cut-away portion of a sphere of akinematic mount, such sphere meeting a conical contact zone within thesensor head. Any shaped piece can be used in place of a sphere.Furthermore, the mount has two arms, orthogonal to one another, onehaving a groove contact zone, the other having a plane contact zone. Thesphere defines the mount's axis of rotation, further with the mirrormounted at or near the center of the sphere then the steering of themirror by some adjustment means results in purely angular motion of thelaser beam at the cantilever depending on which arm is adjusted.Therefore, since the mirror is mounted at or near the center of a sphereand there are at least two means of adjustment of the orientation of thesphere, then the result is nearly independent motion of the laser beam.This makes alignment of the laser easy and intuitive. The kinematicmount is positioned within the sensor head, such having translationalknobs for meeting the groove contact zone and the plane contact zone andfor adjustment of the position of the mirror kinematic mount.

The sensor head also includes a stage kinematic mount which provides forthe adjustment of the entire sensor head with respect to the base of thescanning force microscope. It too includes a groove contact zone, aplane contact zone and a conical contact zone, such being adjustable intwo approximately orthogonal directions in the horizontal plane.Incorporated into the base are adjustable approach screws with sphericaltips for meeting the contact zones of the stage kinematic mount.

Other objects and advantages of the invention will become apparent uponreading the following detailed description with reference to thedrawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an exploded view show a scanning force microscope inaccordance with the preferred embodiment.

FIG. 2 is a schematic diagram of the deflection detection system of thepresent invention.

FIG. 3 shows an expanded view a portion of the apparatus of thepreferred embodiment.

FIG. 4 shows the mirror kinematic mount of the present invention.

FIG. 5 shows the mirror kinematic mount of the present inventionincorporated into the top portion of the apparatus.

FIG. 6 shows a detailed drawing the stage kinematic mount of the presentinvention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

The scanning force microscope of the present invention as shown in FIG.1, has a base portion 10 and a sensor head portion 11. Typically, baseportion 10 houses the sample on sample holder 12 mounted on samplepiezoelectric scanner 13. As stated above, the sample is mounted formovement relative to the probe 14. The probe 14 is mounted so that it isgenerally positioned opposite the sample on a flexible cantilever 16,the continuation of which is deflected according to the surface heightof the sample (see FIG. 2). Such means for positioning the sample holderlaterally 12 relative to the probe 14 is incorporated into the sensorhead 11. The scanning movement of the sample relative to the probe iscontrolled by a servo loop wherein connector 17 and connector 18 are incommunication with the servo loop and the sample piezoelectric scanner13. Position adjustment signals are sent to the movable sample scanner13 accordingly.

A sample scanner 13 may be a tubular piezoelectric device which has acentral electrically continuous portion and an outer portion, dividedinto electrically isolated quadrants. Viewing such a tubularpiezoelectric device from one annular end, the outer portion quadrantsare divided according to 90 degree arcs, one piezoelectric elementoccupying the area of zero degrees to 90 degrees, a second occupying thearea of 90 degrees to 180 degrees, and so on. By applying a voltage tothe tubular piezoelectric device and thereby changing its shape, thesample is moved. When a voltage is applied to the central portion withrespect to the outer quadrants equally, the sample holder 12 effectsvertical movement of the sample mounted upon it. When a voltage isapplied to the outer portions unequally, lateral and vertical movementof the sample as indicated by reference number 15 of FIG. 2 is effected.Such a sample holder is more thoroughly described by Binnig and Smith inReview of Scientific Instruments, August 1986.

FIG. 2 shows a schematic of the deflection detection system whichproduces information utilized by the servo loop for the continualadjustment of sample holder 12 with respect to the probe 14. A reflector20, made of a suitable reflecting material, may be positioned upon theend of the cantilever 16. A laser diode 21 is positioned above and toone side of the probe 14 and reflector 20. The light 25 of the laser 21is first directed to a mirror 22 which in turn reflects the light 25 toreflector 20. The light 25 reflected off of reflector 20 strikesphotodetector 23, such being a split detector. Signals proportional tothe light sensed by each half of detector 23 are subtracted to form asignal proportional to the deflection angle of reflector 20.

The feedback arrangement of the instant invention utilizes the splitphotodetector for comparison, wherein a reference voltage is compared tothe signals described above. The sample is moved up or down by thesample holder 12 corresponding to the deflection of the cantilever, suchmovement ultimately providing the map of the sample.

FIG. 2 shows that there are minimal physical obstructions to visualobservational adjustments of the probe with respect to the sample..Iadd.In one embodiment, as illustrated in FIG. 1, the sensor head mayhave a U-shaped portion 65 which forms a U-shaped opening. As shown inFIG. 1, the probe 14 may be attached to the sensor head such that theprobe 14 is positioned within the U-shaped opening. In this embodiment,as illustrated in FIG. 1, the U-shaped opening may be oriented such thatthe U-shaped portion of the sensor head does not block visualobservation of the probe along an arc extending from a spacesubstantially vertically above the probe to a position adjacent theU-shaped opening which is at substantially the same vertical level asthe probe. .Iaddend.In the preferred embodiment, the top portion of thesensor head has a space 30 (see FIG. 3) which may be covered by aremovable member, such space allowing one to look directly down upon thecantilever to adjust its position with respect to the sample and toadjust the laser alignment on the cantilever.

FIG. 3 shows an expanded view of the sensor head 11 of the preferredembodiment looking up from arrows A of FIG. 1. The optical deflectiondevice and probe of the present invention is housed in the top portion31 of sensor head 11. The probe mounted on cantilever 16 is in turnmounted on tip holder 32, such being fixably mounted within the topportion 31 of sensor head 11.

The means for aligning the deflection device includes securing themirror 22 within a cut away portion 34 of sphere 36 of the mirrorkinematic mount 33. FIG. 4 shows kinematic features of mirror kinematicmount 33 wherein a first arm 37 has groove contact area 38 which meetsball end screw 39 (see FIG. 3) and a second arm 40 has a flat contactarea 41 which meets ball end screw 42. When an adjustment is made to onecontact area, the other contact areas also adjust, avoiding tension inthe system. However, it can also be envisioned that simple slidingsurfaces would suffice if other tension relieving mechanisms wereprovided. Furthermore, alternative kinematic mounts other than sphericalmounts might suffice for sphere 35, for example, flexure mounts.

As shown in FIG. 5, arm 40 is flexibly secured to the top portion 31 byspring 44. Although not shown, arm 37 is also flexibly secured to thetop portion 31 by spring 43. Springs 43 and 44 hold sphere 36 and therest of mirror mount 33 under positive pressure, keeping the assemblytogether. Were the assembly mounted upside down, gravity alone wouldkeep the assembly together.

The means for positioning sphere 36 is placing the sphere 36 in contactwith three spheres 46 which are arranged in a triangular configuration.Such a configuration provides a conical contact zone for kinematicmounting. The means for adjusting the mirror kinematic mount 33 withrespect to the top portion 31 is detector adjustment screw 47 whichprovides translational motion.

By adjusting the position of adjustment screws 47 up or down, the normalof mirror 22 will rotate about the rotational point of the sphere 39 inwhich it is mounted when mounted in the center of the sphere therotation of the normal of the mirror can be performed in an leastindependent motions with minimal translation of the light. This makessteering the laser beam to the cantilever probe easy and intuitive.Because first arm 37 is orthogonal to second arm 40, the light steeredby the mirror 22 will be steered in approximately orthogonal angulardirections.

A second degree of adjustment freedom of the sensor head 11 with respectthe sample is provided by stage kinematic mount 50 having movablecontact portions, for effecting translation of the mount. On a surface51 facing the base 10, the stage mount 50 has a first movable contactportion 52a and conical contact zone 52, a second movable contactportion 53a and groove contact zone 53 and planar contact zone 54 eachof which positioned at corners of a triangle superimposed on the surface51. The position of the contact zones relative to surface 51 isadjustable by translation knobs 56 and 57, wherein knob 56 adjusts theposition of slot 50 relative to surface 51 and knob 57 adjusts theposition of conical contact zone 52 relative to surface 51. FIG. 6 showssurface 51 facing base 10 such that the course adjustment screws 57, 58,59 meet conical contact zone 52, groove contact zone 53 and planarcontact zone 54, respectively. The height of the course adjustmentscrews is adjustable by knurled knobs 60.

The stage mount 50 provides translational motion in two approximatelyorthogonal directions. Therefore, the present invention providesversatility in orientation of the probe relative to the sample as wellas versatility in orientation of the detection deflection system byvirtue of the systems disclosed herein. Furthermore, the presentinvention provides ease in visual observational adjustments of the probewith respect to the sample as well as the laser with respect to theprobe.

In view of the foregoing, it is clear that the object of the presentinvention to provide a scanning microscope in which there are nophysical obstructions to visual observational adjustments of the probewith respect to the sample as well as the laser with respect to theprobe has been achieved. Moreover, the object of the present inventionto provide an optical deflection detection system having fine adjustmentcapabilities has also been achieved by the mirror kinematic mount.Furthermore, the object of providing a scanning microscope havingadjustment capabilities with two degrees of freedom has been achieved byincluding the stage kinematic mount. Finally, the object of providingimproved mechanical rigidity to the apparatus has also been achieved.

While the invention has been herein shown and described in what ispresently conceived to be the most practical and preferred embodiment ofthe invention, it will be apparent to those of ordinary skill in the artthat many modifications thereof may be made within the scope of theinvention, which scope is to be accorded the broadest interpretation ofthe claims so as to encompass all equivalent structures and devices.

We claim: .[.1. A scanning probe microscope apparatus having a sampleholder for holding a sample positioned relative to a probe, suchpositioning being monitored by an optical deflection detection system,comprising: wherein said mirror is mounted within said cut awayportion..]..[.5. An apparatus as recited in claim 3 wherein saidrotatable holder further comprises:a first element positioned betweensaid base portion and said top portion comprising: a first arm connectedto said rotatable holder; a second arm connected to said rotatableholder and orthogonal to said first arm; and wherein positionaladjustment of said first element provides rotation of said rotatableholder which defines rotation of said mirror..]..[.6. An apparatus asrecited in claim 5 wherein said first arm has a first zone for kinematicmounting and wherein said second arm has a second zone for kinematicmounting..]..[.7. An apparatus as recited in claim 6 further comprising:a second element incorporated into said apparatus top portioncomprising: first position means for positioning said rotatable holder;and adjustment means associated with said first contact zone and saidsecond contact zone for adjusting the position of said first elementrelative to said second element..]..[.8. An apparatus as recited inclaim 7 wherein said first position means for positioning said holder isa conical contact zone..]..[.9. An apparatus as recited in claim 7wherein said adjustment means comprises at least one adjustmentscrew..]..[.10. An apparatus as recited in claim 1 wherein means forsteering an optical beam of said deflection detection system,comprising: a reflective cantilever including a probe; a light sourcewhich emits light for reflection off said cantilever, said light obliqueto said sample holder; a mirror in the path of said light, directingsaid light to said cantilever; and a detector for receiving said lightwhich has been reflected off said cantilever..]..[.11. An apparatus asrecited in claim 10 wherein said means for positioning said sampleholder relative to said probe comprises a feedback arrangement whereinsaid detector is a light position sensitive detector which providesfeedback information regarding deflection of said probe relative to saidsample to a control system, such control system involving a servo loopwhich adjusts the position of said sample holder relative to said sensorhead according to said feedback information..]..[.12. An apparatus asrecited in claim 1 wherein said means for adjustably situating saidsensor head relative to said base comprises a movable stage..]..[.13. Anapparatus as recited in claim 12 wherein said movable stage is a stagekinematic mount to said base..]..[.14. An apparatus as recited in claim13 wherein said stage kinematic mount comprises: a third element havinga first contact zone, a second contact zone and a third contact zone,each one of said contact zones positioned at one of the corners of atriangle superimposed on said first element, such third elementincorporated into said top portion and facing said apparatus baseportion; and a fourth element having approach screws being associatedwith at least one of said contact zones, such fourth element beingincorporated into said apparatus base portion and facing said topportion..]..[.15. An apparatus as recited in claim 14 further comprisingsecond position adjustment means for adjusting the position of saidsensor head relative to said base..]..[.16. An apparatus as recited inclaim 15 wherein said second position adjustment means comprises screwmeans incorporated into said sensor head..]..[.17. A scanning probemicroscope apparatus having a sample holder positioned relative to aprobe, such positioning being monitored by an optical deflectiondetection device, comprising: (A) a sensor head including a top portion,such sensor head for housing said probe and said optical deflectiondetection device; (B) a base portion for housing said sample holder; (C)wherein said optical deflection detection system comprises:a reflectivecantilever including a probe; a light source which emits light forreflection off said cantilever; a mirror in the path of said light,directing said light to said cantilever; and a detector for receivingsaid light which has been reflected off said cantilever..]..[.18. Anapparatus as recited in claim 17 further comprising means for aligningsaid optical deflection detection device within said sensorhead..]..[.19. An apparatus as recited in claim 17 wherein said meansfor positioning said sample holder relative to said probe comprises afeedback arrangement wherein said detector is a light position sensitivedetector which provides feedback information regarding deflection ofsaid probe relative to said sample to a control system, such controlsystem involving a servo loop which adjusts the position of said sampleholder relative to said sensor head according to said feedbackinformation..]..[.20. A scanning probe microscope apparatus having asample holder positioned relative to a probe, such positioning beingmonitored by an optical deflection detection device, comprising: asensor head having a top portion, such sensor head for housing saidprobe and said optical deflection detection device and a base portionfor housing said sample holder; and means for aligning said opticaldeflection detection device within said sensor head which allows anunobstructed view of the vicinity of the sample and the probe from aposition above the sample and in a direction approximately perpendicularto the plane of lateral scanning of the sample..]..[.21. An apparatus asrecited in claim 20 wherein said means for aligning said opticaldeflection detection system comprises a mirror in said deflectiondetection system's optical beam's path..]..[.22. An apparatus as recitedin claim 21 wherein said mirror is situated at approximately therotational center of a rotatable holder..]..[.23. An apparatus asrecited in claim 22 wherein said rotatable holder is a sphere having acut away portion and wherein said mirror is mounted within said cut awayportion..]..[.24. An apparatus as recited in claim 22 wherein saidrotatable holder further comprises:a first element positioned betweensaid base portion and said top portion comprising:a first arm connectedto said rotatable holder; a second arm connected to said rotatableholder and orthogonal to said first arm; and wherein positionaladjustment of said first element provides rotation of said rotatableholder which defines rotation of said mirror..]..[.25. An apparatus asrecited in claim 24 wherein said first arm has a first zone forkinematic mounting and wherein said second arm has a second zone forkinematic mounting..]..[.26. An apparatus as recited in claim 25 furthercomprising: a second element incorporated into said apparatus topportion comprising:position means for positioning said rotatable holder;and adjustment means associated with said first contact zone and saidsecond contact zone for adjusting the position of said first elementrelative to said second element..]..[.27. An apparatus as recited inclaim 26 wherein said position means for positioning said holder is aconical contact zone..]..[.28. An apparatus as recited in claim 26wherein said adjustment means comprises at least one adjustmentscrew..]..[.29. A scanning probe microscope apparatus having a sampleholder positioned relative to a probe, comprising: a sensor head forhousing said probe; a base portion for housing said sample holder; andmeans for adjustably situating said sensor head relative to said base,such means comprising a stage kinematic mount..]..[.30. An apparatus asrecited in claim 29 wherein said stage kinematic mount comprises: asensor head element incorporated into said sensor head and facing saidapparatus base portion, such element having a first contact zone on amoveable first contact portion, a second contact zone on a moveablesecond contact portion and a third contact zone, each one of saidcontact zones positioned at one of the corners of a trianglesuperimposed on said element; and a base element incorporated into saidapparatus base portion and facing said sensor head element, such elementhaving approach screws associated with at least one of said contactzones..]..[.31. An apparatus as recited in claim 30 further comprisingposition adjustment means for adjusting the position at least one ofsaid moveable contact portions relative to said sensor head..]..[.32. Anapparatus as recited in claim 31 wherein said position adjustment meanscomprises screw means incorporated into said sensor head..]..[.33. Anapparatus as recited in claim 30 wherein said first contact zone is aslot and said second contact zone is a cone..]..Iadd.34. A scanningprobe microscope sensor head comprising:a probe; a light source; adetector; and a mount for removably mounting the sensor head on a baseand for adjusting the position of the probe relative to a sample on thebase; the sensor head having a space substantially vertically above theprobe, the light source and detector being arranged on the sensor headto enable visual observation of the probe from the space substantiallyvertically above the probe without removal of the light source ordetector. .Iaddend..Iadd.35. A scanning probe microscope sensor headaccording to claim 34 wherein there are no physical obstructions betweenthe probe and the space that prevent visual observation of the probefrom the space substantially vertically above the probe..Iaddend..Iadd.36. A scanning probe microscope sensor head according toclaim 34 wherein the detector is an optical detector. .Iaddend..Iadd.37.A scanning probe microscope sensor head according to claim 34, thesensor head further including a mirror for directing light emitted bythe light source to the probe. .Iaddend..Iadd.38. A scanning probemicroscope sensor head according to claim 34, the light source beingpositioned vertically above and to one side of the probe..Iaddend..Iadd.39. A scanning probe microscope sensor head according toclaim 38, the sensor head further including a mirror for directing lightemitted by the light source to the probe. .Iaddend..Iadd. . A scanningprobe microscope sensor head according to claim 38 wherein there are nophysical obstructions between the probe and the space that preventvisual observation of the probe from the space substantially verticallyabove the probe. .Iaddend..Iadd.41. A scanning probe microscopeaccording to claim 38, the detector being an optical detector..Iaddend..Iadd.42. A scanning probe microscope sensor head according toclaim 34, the sensor head having a U-shaped portion forming a U-shapedopening within which the probe is positioned, the U-shaped opening beingoriented such that the U-shaped portion of the sensor head does notblock visual observation of the probe along an arc extending from aspace substantially vertically above the probe to a position adjacentthe U-shaped opening which is at substantially the same vertical levelas the probe. .Iaddend..Iadd.43. A scanning probe microscope sensor headaccording to claim 42, the light source being positioned verticallyabove and to one side of the probe. .Iaddend..Iadd.44. A scanning probemicroscope sensor head according to claim 42 wherein there are nophysical obstructions between the probe and the space that preventvisual observation of the probe from the space substantially verticallyabove the probe. .Iaddend..Iadd.45. A scanning probe microscope sensorhead according to claim 42 wherein the sensor head further includes amirror for directing light emitted by the light source to the probe..Iaddend..Iadd.46. A scanning probe microscope sensor head according toclaim 34 wherein the sensor head mount is a stage kinematic mount..Iaddend..Iadd.47. A scanning probe microscope sensor head according toclaim 46 wherein the stage kinematic mount includes a mounting elementon the sensor head and facing the base having a first contact zone on amoveable first contact potion, a second contact zone on a moveablesecond contact portion and a third contact zone, each one of saidcontact zones being positioned at one of the corners of a trianglesuperimposed on the mounting element. .Iaddend..Iadd.48. A scanningprobe microscope sensor head according to claim 47 wherein the sensorhead further includes a position adjustment mechanism for adjusting theposition of at least one of the moveable contact portions relative tothe sensor head. .Iaddend..Iadd.49. A scanning probe microscope sensorhead according to claim 48 wherein the position adjustment mechanismincludes a screw incorporated into the sensor head. .Iaddend..Iadd.50. Ascanning probe microscope sensor head according to claim 49 wherein thefirst contact zone is a slot and the second contact zone is a cone..Iaddend..Iadd.51. An apparatus as recited in claim 37 wherein saidmirror is situated at approximately the rotational center of a rotatableholder. .Iaddend..Iadd.52. An apparatus as recited in claim 51 whereinsaid rotatable holder is a sphere having a cut away portion and whereinsaid mirror is mounted within said cut away portion. .Iaddend..Iadd.53.An apparatus as recited in claim 51 wherein said rotatable holderfurther comprises:a first element positioned between said base portionand said top portion comprising:a first arm connected to said rotatableholder; a second arm connected to said rotatable holder and orthogonalto said first arm; and wherein positional adjustment of said firstelement provides rotation of said rotatable holder which definesrotation of said mirror. .Iaddend..Iadd.54. An apparatus as recited inclaim 53 wherein said first arm has a first zone for kinematic mountingand wherein said second arm has a second zone for kinematic mounting..Iaddend..Iadd.55. An apparatus as recited in claim 54 furthercomprising: a second element incorporated into said apparatus topportion comprising: first position means for positioning said rotatableholder; and adjustment means associated with said first contact zone andsaid second contact zone for adjusting the position of said firstelement relative to said second element. .Iaddend..Iadd.56. An apparatusas recited in claim 55 wherein said first position means for positioningsaid holder is a conical contact zone. .Iaddend..Iadd.57. An apparatusas recited in claim 55 wherein said adjustment means comprises at leastone adjustment screw. .Iaddend..Iadd. . A scanning probe microscopecomprising:a base for housing a sample; and a sensor head including aprobe, a light source, a detector, and a mount for removably mountingthe sensor head on the base and for adjusting the position of the proberelative to the sample; the sensor head having a space substantiallyvertically above the probe, the light source and detector being arrangedon the sensor head so as to enable visual observation of the probe fromthe space substantially vertically above the probe without removal ofthe light source or detector. .Iaddend..Iadd.59. A scanning probemicroscope according to claim 58 wherein the sensor head furtherincludes a mirror for directing light emitted by the light source to theprobe. .Iaddend..Iadd.60. An apparatus as recited in claim 59 whereinsaid mirror is situated at approximately the rotational center of arotatable holder. .Iaddend..Iadd.61. An apparatus as recited in claim 60wherein said rotatable holder is a sphere having a cut away portion andwherein said mirror is mounted within said cut away portion..Iaddend..Iadd.62. An apparatus as recited in claim 60 wherein saidrotatable holder further comprises:a first element positioned betweensaid base portion and said top portion comprising:a first arm connectedto said rotatable holder; a second arm connected to said rotatableholder and orthogonal to said first arm; and wherein positionaladjustment of said first element provides rotation of said rotatableholder which defines rotation of said mirror. .Iaddend..Iadd.63. Anapparatus as recited in claim 62 wherein said first arm has a first zonefor kinematic mounting and wherein said second arm has a second zone forkinematic mounting. .Iaddend..Iadd.64. An apparatus as recited in claim63 further comprising: a second element incorporated into said apparatustop portion comprising:position means for positioning said rotatableholder; and adjustment means associated with said first contact zone andsaid second contact zone for adjusting the position of said firstelement relative to said second element. .Iaddend..Iadd.65. An apparatusas recited in claim 64 wherein said position means for positioning saidholder is a conical contact zone. .Iaddend..Iadd.66. An apparatus asrecited in claim 64 wherein said adjustment means comprises at least oneadjustment screw. .Iaddend..Iadd.67. A scanning probe microscopeaccording to claim 58, the light source being positioned verticallyabove and to one side of the probe. .Iaddend..Iadd.68. A scanning probemicroscope according to claim 67, the sensor head having a U-shapedportion forming a U-shaped opening within which the probe is positioned,the U-shaped opening being oriented such that the U-shaped portion ofthe sensor head does not block visual observation of the probe along anarc extending from a space substantially vertically above the probe to aposition adjacent the U-shaped opening which is at substantially thesame vertical level as the probe. .Iaddend..Iadd.69. A scanning probemicroscope according to claim 68, the light source being positionedvertically above and to one side of the probe. .Iaddend..Iadd.70. Ascanning probe microscope according to claim 68 wherein there are nophysical obstructions between the probe and the space that preventvisual observation of the probe from the space substantially verticallyabove the probe. .Iaddend..Iadd.71. A scanning probe microscopeaccording to claim 68 wherein the sensor head further includes a mirrorfor directing light emitted by the light source to the probe..Iaddend..Iadd.72. A scanning probe microscope according to claim 58,the scanning probe microscope further including a positioning member forpositioning the sample holder relative to the probe. .Iaddend..Iadd. Ascanning probe microscope according to claim 58 wherein there are nophysical obstructions between the probe and the space that preventvisual observation of the probe from the space substantially verticallyabove the probe. .Iaddend..Iadd.74. A scanning probe microscopeaccording to claim 58 wherein the sensor head mount is a stage kinematicmount. .Iaddend..Iadd.75. A scanning probe microscope according to claim74 whereinthe stage kinematic mount includes a mounting element on thesensor head and facing the base having a first contact zone on amoveable first contact portion, a second contact zone on a moveablesecond contact portion and a third contact zone, each one of saidcontact zones being positioned at one of the corners of a trianglesuperimposed on the mounting element, and the base includes a basemounting element facing the sensor head mount and having approach screwsassociated with at least one of the contact zones. .Iaddend..Iadd.76. Ascanning probe microscope according to claim 75 wherein the sensor headfurther includes a position adjustment mechanism for adjusting theposition of at least one of the moveable contact portions relative tothe sensor head. .Iaddend..Iadd.77. A scanning probe microscopeaccording to claim 76 wherein the position adjustment mechanism includesa screw incorporated into the sensor head. .Iaddend..Iadd.78. A scanningprobe microscope according to claim 77 wherein the first contact zone isa slot and the second contact zone is a cone. .Iaddend..Iadd.79. Ascanning probe microscope sensor head comprising: a probe; a mount forremovably mounting the sensor head on a base and for adjusting theposition of the probe relative to a sample on the base; and a U-shapedportion forming a U-shaped opening within which the probe is positioned,the U-shaped opening being oriented such that the U-shaped portion ofthe sensor head does not block visual observation of the probe along anarc extending from a space substantially vertically above the probe to aposition adjacent the U-shaped opening which is at substantially thesame vertical level as the probe. .Iaddend.